Yes, at surface it looks like re-inventing the web/html, but to use HTML for defining app you would need to add all the native elements as HTML tags to the voca

Yes, at surface it looks like re-inventing the web/html, but to use HTML for defining app you would need to add all the native elements as HTML tags to the vocabulary and that would be a lot. HTML was made to make hypertext with things which were imagined in early 90s, NAML (native app markup language) 25 yrs later should support all the bells and whistles we expect from native app UX 25 years later. I would say attempts to reuse/extend HTML for native app UX definition (Titanium, React Native etc) are more terrible hacks than creating new clean room markup language as here is done.